Humayun is the chief researcher behind the world's first commercially available artificial retina, a breakthrough that literally helps the blind see.

The artificial retina — technically, a retinal prosthesis — is the culmination of nearly 20 years of work. It works like this: A user wears special glasses equipped with a tiny camera that captures images of whatever it's pointed at. Those images are then beamed through a microantenna into a watch-battery-sized electronic array implanted inside the user's eye. Electrodes in the array stimulate the eye's retinal cells, generating a pattern of blacks, whites and grays "seen" by the user's brain.

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It only roughly approximates the original image, and is a far cry from true vision, but it's enough to reveal where a door or bus stop is, or even to make letters legible for some users.

The prosthesis works only on people blinded by retinitis pigmentosa, a disease that damages the retina's rods and cones while leaving the optic nerve intact. Still, that describes as many as 300,000 people in Europe and the U.S. combined. The implant, dubbed the Argus II, was cleared for sale in Europe this year and awaits U.S. Food and Drug Administration approval.

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Despite all the ink spilled and video aired since the artificial retinas hit the market, hardly a word has been said in public about Humayun's next project. He's adapting the technology behind the implants to a range of other uses that he believes will affect far more people and spur the growth of the emerging field of bioelectronics — the science of implanting tiny, helpful devices in the body.

"This technology can be huge," he says, "much bigger than retinal implants."

Humayun is a solidly built man with graying sideburns supporting a thick mass of slightly tousled black hair. We're sitting in his office at the University of Southern California, a comfortably sized room bedecked with framed copies of his extensive collection of degrees and patents and a wall-sized whiteboard covered with diagrams and figures.

Humayun is understandably proud of his invention. But he walks me out to the foyer of his research center to point out that the lettering on the wall doesn't say anything about eyes; it says "Bioelectronic Research Lab." Artificial retinas are just the first example of how he'll apply that science. "All the focus has been on the retinal prosthesis, but my vision has always been something bigger," he says.

The hardest part of developing the artificial retina, he says, was designing a package small and sturdy enough to work inside a human eye. All of the gadget's pieces have to be excruciatingly tiny and hermetically sealed.

"The eye is salty, hot and full of enzymes that tend to break down whatever you put in there," says Brian Mech, a spokesperson for Second Sight, the company bringing the prosthesis to market. "It's like shrinking a TV to the size of a pill, throwing it in the ocean and saying it needs to work for 20 years."

The next-biggest challenge was designing a telemetric system to transmit information into the array. "You can't buy that kind of engineering off the shelf," Humayun says. "We had to develop it all ourselves."

Having accomplished that, Humayun sees all kinds of ways that technology can be used elsewhere.

Other types of eye treatments are an obvious first step. For instance, there's only one way to treat the hundreds of thousands of eye patients suffering from macular degeneration: Once a month, jab them in the eye with a syringe. Patients don't exactly enjoy that, so, many skip their treatments. Humayun is working with a private company founded by one of his students to adapt his array into an implant that would hold several months' worth of medication and squirt precisely timed and measured doses of medication directly into the patient's eye.

Similar devices could do the same thing for glaucoma patients, who now have to put in daily eye drops. Glaucoma could be prevented from developing in the first place by implants equipped with tiny sensors that measure the pressure of fluids inside a user's eye, releasing excess fluid or injecting preventive drugs as needed.

Outside the eye, Humayun is working with another company to use it in a Band-Aid-like patch that could deliver insulin through the skin, saving diabetics from having to inject themselves.

Another project he's working on uses spinal implants to stimulate the nervous system, helping disabled people to walk. That device has been tried on only one human subject so far, says Yu-Chong Tai, a California Institute of Technology electrical engineering professor who works closely with Humayun, but the results are promising. "After three months, the patient was able to generate small stepping motions," Tai says.

Ultimately, he says, "this technology will go to the brain, no doubt about it." Tai foresees implants inside people's skulls that will help epileptics control their seizures and physically disabled people control wheelchairs or robot limbs with their minds.

Of course, there's no guarantee that all — or any — of these potential medical miracles will actually reach the market. They're all in various stages of research and development, and there are rival companies working on their own versions of some of them. Moreover, any procedure that involves planting an artificial gizmo inside the body carries considerable risks. Some of Humayun's test subjects had their retinas badly damaged when the electrodes were improperly attached. "Things could be 10 times worse when you're talking about spinal cords," Tai says.

Humayun is well aware of the obstacles ahead — after all, it took him decades to develop the artificial retina. But he's confident about what's coming. "I believe bioelectronics will change how we practice medicine."

That may sound a tad grandiose, but as his subjects can attest, seeing is believing.

Vince Beiser is an award-winning writer whose work has appeared in Wired, Harper's, TheAtlantic, Mother Jones, and Rolling Stone, among other publications. A graduate of the University of California–Berkeley, he lives in Los Angeles.